Three elements are commonly accepted as definitive of a barbecue cooking process. First, cooking is performed at relatively low temperatures, such as 200 to 300° F., for relatively long periods of time, such as 6 to 20 hours. These temperatures and times reduce temperature gradients within the meat and thereby produce a more uniform cooking process throughout the meat being cooked, and also permit fats and connective tissues to break down, thereby tenderizing the meat.
Second, heat is transferred to the meat primarily through convection of heated air rather than radiation, as in broiling and grilling, or conduction, as in frying, again to reduce temperature gradients within the meat and thereby produce a more uniform cooking process throughout the meat being cooked. In essence, the meat is baked.
Third, heat is produced by the combustion of wood and the baking atmosphere imparts the flavors therefrom to the meat being cooked. This element is the most difficult to satisfy in combination with the first two and merits a brief discussion of wood and wood fires.
Wood is a highly complex organic material, but for the purposes of cooking, it can be modeled simply as the sum of three components: water, volatile organic compounds, known collectively as wood-gas, and carbon, known as charcoal.
In a wood fire, three processes are underway simultaneously. First, newly added wood desiccates. Second, the dry wood decomposes into two fuels: wood-gas and charcoal. Third, provided that sufficient heat and oxygen are present, the two fuels burn: wood-gas as a visible flame and charcoal as glowing embers.
If sufficient heat or oxygen are not available, all or part of the fire will smolder, producing wood-gas that no flame is consuming. The noxious, unburned wood-gas will then condense as wood creosote, a black and tarry film, on any relatively cool surface it encounters. The surface of meat is ideal for this condensation, which accumulates over time and therefore affects larger cuts that cook for longer periods. The film's oily components leach deeply into the meat, rendering it blackened and unpalatable.